JPS63106940A - Optical recording medium - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium, and more particularly to an improvement in a rewritable optical recording medium.

[Prior Art] Optical recording media have advantages such as not being subject to abrasion and deterioration because there is no contact between the recording head and the reading head. Among these various optical recording media, heat-mortar optical recording media do not require image processing in a darkroom, and therefore, application development for, for example, optical carts, optical disks, and optical tapes is becoming active.

Such heat-mortar optical recording media convert recording light (beam) into heat and utilize optical modulation by the beam irradiation section.
There is also a method in which small holes called pits are recorded according to information by melting or removing the portion, and the presence or absence of these pits can be detected using readout light.

These write methods generally use a laser beam to melt and evaporate the recording portion of the medium to create a hole, and cannot be rewritten. On the other hand, there are known examples of rewritable optical recording media that utilize the photodarkening phenomenon of amorphous chalcogenide; such amorphous chalcogenide materials generally have low recording sensitivity;
Furthermore, the optical absorption edge is on the relatively short wavelength side, and furthermore, the absorption is small at wavelengths near the absorption edge, so the recording sensitivity for long wavelength light is extremely low.

In general, the above-mentioned laser light is most suitable as a light source for this type of optical recording because the light beam can be narrowed down to a minimum size, and semiconductor lasers in particular are attracting attention because they have the advantage of being extremely compact. However, the wavelength range is 750 to 800 nm or more, and will probably be around 700 nm in the future, which is a relatively long wavelength. Furthermore, the wavelength range of the He--Ne laser, which is generally small and highly stable, is 632.8 nm. Furthermore, short wavelength lasers include Ar, Kr, etc., making them slightly more unstable and extremely large. That is, it can be said that the amorphous chalcogenide described above has significant restrictions on the light source that can be used, and moreover, it is almost impossible to miniaturize the amorphous chalcogenide.

Other well-known materials include magneto-optical materials. Although there are few restrictions regarding the light source used, the problem is that the so-called magnetic Kerr effect is used during readout, and the effect is small and the readout S/N ratio is very poor.

Another example is a recording medium that combines a thermoplastic material on a substrate with a conductive layer, and after uniformly charging, there is a method of recording signals with a thermal head, but optical recording is possible because recording with a thermal head is possible. Compared to this, it is difficult to say that it is sufficient to meet the demands of high-density recording.

As described above, the reality is that many conventional recording media, especially optical recording media, do not necessarily have satisfactory rewritability and performance characteristics during rewriting.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and includes at least a dye or a pigment that is a light absorbing material and a photoconductive material, and a thermosetting material on a substrate having a conductive layer. An optical recording medium having an optical recording layer containing a plastic material has significantly improved recording, reproducing, and erasing sensitivity. The present invention was completed after discovering that it is possible to realize a digital recording medium.

[Means for Solving the Problems] and [Operation] That is, the present invention uniformly charges the optical recording layer of an optical recording medium having an optical recording layer on a substrate having a conductive layer, and further charges the optical recording layer. In an optical recording medium in which recording is performed by exposing a signal to form a change in the shape of concaves and convexes corresponding to an optical signal, the optical recording layer includes at least a dye or pigment that is a light absorbing material and a photoconductive material, and a thermoplastic material. An optical recording medium characterized by containing:

The present invention is an optical recording medium having an optical recording layer containing at least a dye or pigment, which is a light absorbing material and a photoconductive material, and a thermoplastic material, on a substrate having a conductive layer,
In particular, it is an optical recording medium in which the dye or pigment, which is the light absorbing material and photoconductive material, has absorption in the near infrared region, which is the oscillation wavelength of a semiconductor laser.

Hereinafter, the present invention will be specifically explained based on the drawings.

FIG. 1 is a sectional view showing an example of the optical recording medium of the present invention, in which 1 is a substrate, 2 is a conductive layer, 3 is an optical recording layer, 3
a is a dye or pigment which is a light absorbing material and a photoconductive material, and 3b is a thermoplastic material.

When the recording readout method is a transmissive type, it is necessary to use a smooth transparent substrate.2 When the recording readout method is a reflective type, an opaque substrate may be used.Various materials can be used for the substrate.0For example, 1 Usually, various glasses, various ceramics, polymethacrylic resin, polyacrylic resin,
It is preferable to use various resins such as polycarbonate resin, and the shape and dimensions may be in the form of disks, sheets, tapes, drums, etc. depending on the intended use.

Further, as the conductive layer 2, a transparent conductive layer such as an ITO Nesa film is generally used, or in the case of a reflective type, a conductive layer such as a metal or metal oxide film may be used.

Next, as the thermoplastic material 3b in the optical recording layer 3, for example, polystyrene, vinyl chloride resin, vinyl acetate resin, ABS s1 resin, acrylic resin, polyethylene,
Examples include low molecular weight polymers such as polypropylene, fluororesin, polyamide resin, acetal resin, and polycarbonate. Furthermore, among the thermoplastic materials mentioned above,
Molecule MM.

is 1000 to 10000, and the molecular weight distribution Mw/Ml
is ≦1.2, and it is preferable to use a low molecular weight polymer whose dispersion is close to monodisperse. Thermoplastic materials tend to soften or melt and deform due to a temperature rise in the area irradiated with recording light to form recording pits.

In this case, the molecular weight M of the thermoplastic material 3b is 1
If it is less than 000, it is liquid or the softening point is too low to withstand repeated use.
If it exceeds ooo, is erasing and rewriting possible? The C/N (carrier/noise) ratio during reading becomes poor due to defective recording pits, especially the peripheral portions, caused by light irradiation. In addition, when repeatedly erasing and rewriting many times,
This C/N ratio gradually deteriorates.

On the other hand, when the molecular weight distribution M, /Mn>1.2, the molecular weight is non-uniform, so the deformed state becomes uneven depending on the recorded location, and furthermore, it becomes difficult to return to the original state even when erasing.

On the other hand, one molecule IkFaw is 1000 to 10,000
0, and when the molecular weight distribution Fa, /Pa, is ≦1.2, recording pits with an extremely high C/N ratio can be obtained, and it is possible to erase and rewrite many times. There is little deterioration.

Such thermoplastic materials can be easily obtained by radical telomerization, ion telomerization, thermal polymerization, polymer depolymerization, mechanical cutting of polymers, etc., or can be obtained by using commercially available materials. It can also be used after being separated by molecular weight.

On the other hand, the optical recording medium M3 contains a dye or pigment 3a which is a light absorbing material and a photoconductive material along with the thermoplastic material 3b as described above.

The dye or pigment 3a, which is a light absorbing material and a photoconductive material, exhibits a large light absorption rate for recording light.

In the light irradiation part, light energy is absorbed and converted into thermal energy, and as the temperature rises, a charge is uniformly applied to the optical recording layer by a corona discharger or the like, and the light is absorbed in the light irradiation part and a charge is generated; Changes in electric field cause changes in electrical attractive force.

Therefore, various known dyes or pigments can be used depending on the wavelength of the recording light. In particular, when using a lightweight and low-cost semiconductor laser as the recording light, dyes or pigments that have light absorption and photoconductivity in the near-infrared region include, for example, CdS, ZnO1Ti, etc. containing impurities and sensitizers.
Including inorganic pigments such as O□, organic pigments such as azo and phthalocyanine, and cyanine, merocyanine, triphenylmethane, naphthoquinone, xanthine, squalium, azulene, methine, and biryllium, azo,
Stilbene phthalocyanine direct dyes, azo, anthraquinone, triphenylmethane, xanthine, azine acid dyes, cyanine, azo, azine, triphenylmethane, azulene, methine, pyrylium basic dyes,
Azo, anthraquinone, xanthine, triphenylmethane mordants, acid mordant dyes, anthraquinones, indigoid vat dyes, azo, anthraquinone, phthalocyanine, triphenylmethane oil-soluble dyes, sulfur dyes, and metals such as dithiols. Examples include organic dyes such as complexes.

In addition, the thermoplastic material 3 contained in the optical recording layer
b and a dye or pigment 3a which is a light absorbing material and a photoconductive material
The content ratio is generally 0.01 to 100 parts by weight, preferably 0.1 parts by weight per 10 parts by weight of the thermoplastic material.
It can be selected from a wide range within the range of 20 parts by weight.

Such an optical recording layer can be coated onto the substrate by various known methods such as spinner coating, dipping coating, and roll coating. Moreover, the film thickness of the optical recording layer is 0.01 pm~
A thickness of 11 cm is preferred.

In addition, by incorporating additives such as various oligomers and polymers into such an optical recording layer, it is possible to improve the adhesion to the substrate, improve the coating property, and change the softening temperature. In addition, various plasticizers, surfactants, antistatic agents, lubricants, flame retardants, ultraviolet absorbers, antioxidants, stabilizers, dispersants, etc. can be contained.

Further, a reflective layer and an undercoat layer may be provided on the substrate having the conductive layer, if necessary, and an optical recording layer may be provided thereon.

Next, an example of the recording medium writing and erasing method according to the present invention will be explained using FIG.

First, as shown in FIG. 2(a), the surface of the recording medium is uniformly charged by corona discharge, and then, as shown in FIG. 2(b) or 2(c), the optical recording layer side or A laser beam 4 is irradiated onto the part to be written from the substrate side. Light is absorbed into the dye or pigment 3a, which is a light absorbing material and photoconductive material, in the area irradiated with the laser light, and the thermoplastic material 3b is heated to a temperature higher than its softening point (glass transition point), and the generated electric charge is As it moves through the optical recording layer, the arrangement of the electric field changes, the electric attractive force increases, and thickness deformation occurs.
The record is fixed by cooling it as it is, and the record is fixed as shown in Figure 2 (
As shown in d), uneven recording bits are formed.

In this case, after light irradiation as shown in FIG. 2(e).

Recharging can also facilitate thickness deformation. Further, in the recording described above, charging and laser light irradiation may be performed simultaneously.

Then, by further uniformly reheating, the surface of the recorded bit having an uneven shape is remelted.

It returns to a flat state as shown in FIG. 2(f).

As heating for erasing, any of laser light irradiation, heating with various heaters, infrared lamp irradiation, etc. may be used.

Further, a protective layer or the like may be provided on the recording layer.

Even if such erasing and writing are repeated, the pits always show a good shape, reading with a high C/N ratio is performed, and the surface always returns to a flat surface after erasing, so the number of repetitions can be increased. Erasing and writing can always be performed reliably and satisfactorily no matter what happens.

[Example code] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 3 Polystyrene [Picolastic D-100 (manufactured by Exxon Chemical Co., Ltd.) was used as a thermoplastic material.

y1w = 1500) ] 110 weight and a dye represented by the following structural formula I as a dye that is a light absorbing material and a photoconductive material 0
．． 8 parts by weight of fTO was dispersed in methyl ethyl ketone, and this dispersion was used as a conductive layer to deposit fTO.
The optical recording medium of Example 1 with a dry film thickness of 0.8 mm was prepared by coating on a 2 liter thick glass substrate using a spinner coating method.

Structural formula I H3 Example 2 As a thermoplastic material, polystyrene [Docolastic D-125 (manufactured by Exxon Chemical Co., Ltd., M) was used.

= 3,000) 110 parts by weight and 5 parts by weight of the pigment shown in the structural diagram (■) below as a pigment that is a light absorbing material and a photoconductive material were dispersed in methyl ethyl ketone, and this dispersion was used as a conductive layer and ITO was vapor-deposited. It was coated on a glass substrate with a thickness of 1.2■■ using a spinner coating method, and the dry film thickness was 1.
An optical recording medium of Example 2 of 5μ tumor was prepared.

Structural formula ■ Example 3 Polystyrene [Picolastic E-125 (manufactured by Exxon Chemical ■, Mw = 6.0) was used as a thermoplastic material.
0[1)] ε-type copper phthalocyanine (manufactured by Toyo Ink ■,
) 2 parts by weight was dispersed in methyl ethyl ketone, and this dispersion was used as a conductive layer to deposit ITO.
．． Coated on a 2mm thick glass substrate using a spinner coating method,
The dry film thickness 2. An optical recording medium of Example 3 of OB was produced.

Example 4 Polystyrene [Picolastic D-100 (manufactured by Exxon Chemical Co., Ltd., Mw: = 1,5
00) 110 parts by weight of a dye that is a light absorbing material and a photoconductive material and is represented by the following structural formula m is dispersed in methyl ethyl ketone, and this dispersion is used as a conductive layer to form TerTO! The optical recording medium of Example 4 was prepared by applying the coating onto a glass substrate of 200 mmφ and 1.2 mm g using a spinner coating method to have a dry film thickness of 1.0%.

Structural Formula ■ In the optical recording media of Examples 1 to 4 thus obtained, the surface of the optical recording layer is uniformly negatively charged while rotating each medium at 900 rpm, and the oscillation wavelength is 830 nm and the output is A semiconductor laser of 8 mW (on the short surface) was focused on 1.5 g +++, and the recording frequency IMl (z
The semiconductor laser beam was irradiated with 0, then the output was 1 +W
Using a semiconductor laser (on the short surface), its transmitted light was detected by a photodiode, and its C/N ratio was measured.

The results are shown in Table 1.

Table 1 From the results shown in Table 1, it is recognized that the optical recording medium of the present invention has a good C/N ratio. Also,
When the surface of the recording layer of the above medium was observed under a microscope, it was found that in Examples 1 to 4, uniform pits were formed that were concave at the center of light irradiation and convex at the outer periphery.

Furthermore, the optical recording medium 1 of Examples 1 to 4 recorded
While rotating at 00 rpm, a semiconductor laser with an oscillation wavelength of 83001 and an output of 10 mW (on the short surface) is focused at 5μ increments and irradiated onto the recording area for erasing. This was repeated 000 times. Table 2 shows the change in C/N ratio at that time.

Table 2 From the results in Table 2, Examples 1 to 4 had a repetition rate of 1.000
It is observed that an almost stable C/N ratio can be obtained even after the cycle.

Example 5 2005mφ, 1.2mm with Au vapor deposited as a conductive layer
Example 5 The dispersion used in Example 1 was coated on a thick glass substrate using a spinner coating method, and a layer with a dry film thickness of 0.7 μm was obtained.
An optical recording medium was prepared.

Recording was performed on the optical recording medium of Example 5 produced as described above in the same manner as in Example 1.

Then, using a semiconductor laser with an output of 1 mW (on the medium surface), the reflected light is detected by a photodetector, and the C
The 1M ratio was measured. Furthermore, in the same manner as in Example 1,
Erasing and writing were repeated 1000 times. Table 3 shows the changes in the C/N ratio.

Table 3 From the results in Table 3, it is confirmed that even in reflective readout, a good C/N ratio can be obtained even after 1000 times of erasing and writing.

[Effects of the Invention] As explained above, according to the optical recording medium of the present invention, the shape of the recording pits is extremely good in terms of the repeatability of writing and erasing with laser light, and the shape of the recording pits is very good when using transmitted light for reading. A high C/N ratio can also be obtained using reflected light.

Furthermore, since erasing is always performed stably, even if erasing and rewriting are repeated many times, sufficiently stable recording can be performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the optical recording medium of the present invention;
2(a) to 2(Cf) are explanatory diagrams showing an example of a writing and erasing method for an optical recording medium. l... Substrate 2... Conductive layer 3... Optical recording layer 3a... Dye or pigment 3b... Thermoplastic material 4... Laser light

Claims (3)

[Claims] (1) By uniformly charging the optical recording layer of an optical recording medium having an optical recording layer on a substrate having a conductive layer and further exposing the optical signal, the shape of the unevenness changes in response to the optical signal. 1. An optical recording medium in which recording is performed by forming an optical recording medium, wherein the optical recording layer contains at least a dye or pigment that is a light absorbing material and a photoconductive material, and a thermoplastic material. (2) The optical recording medium according to claim 1, wherein the dye or pigment that is the light absorbing material and photoconductive material has absorption in the near infrared region. (3) The optical recording medium according to claim 1, wherein the exposure of the optical signal uses a semiconductor laser as a light source.